1. For the simple syrup: Combine the sugar, thyme and 2 cups water in a medium saucepan over medium heat. Cook, stirring occasionally, until the sugar has dissolved, about 2 minutes. Remove from the heat and let sit for 20 minutes to infuse. Strain the syrup into a container and discard the thyme.
2. For the whiskey sour: Combine the bourbon, Meyer lemon juice and 1 1/2 ounces thyme simple syrup in a cocktail shaker with ice. Shake well, then strain into a cocktail glass. Garnish with a lemon twist and a thyme sprig. Serve.